On web form button, prevent user from clicking the button mo

Question

In a vb.net 2010 web form application that uses web form controls, there is a 'process' button where the user can click on the button lots of times.
This causes problems in the application for every time the button is clicked on, that many records are created in the sql server 2016 database.

I would like a solution on how to prevent the user from clicking on the button more than one time. I have a 'click button' code to catch when the button is clixked right away.
But I would like to know what I can do so the user knows they cannot click the button more than once:
1. I could make the button invisible.
2. However I would either like to have a popup message and/or somewhere on the webpage saying they can click on the process button only one time.
Thus can you show me the code on preferable setting up a popup menu? If not, can you show me the code on how to display the message on the web form page?